1. Field of the Invention
This invention relates to a connector for coupling metal or resin pipes or tubes having a relatively small diameter not exceeding about 20 mm which are often used to form a path for the supply of a fluid, such as oil or air, to or in automobiles, machines or equipment.
2. Description of the Prior Art
A known connector is disclosed in Japanese Utility Model Application laid open under No. 82192/1986. It comprises a collar 21 having an open-ended large-diameter rear portion 22 with a large inside diameter, and a pawl 23 formed by a part of the wall of the large-diameter portion bent radially inwardly and extending toward a small-diameter front portion 22' with a small inside diameter, a seal ring 24 fitted in an annular groove 25 formed in the inner surface of the small-diameter portion 22', and a pipe P.sub.1 having a flange P.sub.1 ' held by the pawl 23, and an inner tubular portion P.sub.1 " held in intimate contact with the seal ring 24, as shown in FIG. 28 of the accompanying drawings.
This connector has, however, a number of drawbacks. As the flange P.sub.1 ' forms an integral part of the pipe P.sub.1, it is necessary to employ a pipe having a large wall thickness and cut away a substantial portion of its wall thickness to form a flange having a large outside diameter. As a matter of fact, however, it is impossible to form the flange P.sub.1 ' with a diameter which is sufficiently large to ensure that it be held firmly in position by the pawl 23, so that there may not be any displacement of the flange and the pawl from each other when they are vibrated. The work of cutting away a substantial portion of the pipe wall is likely to bring about a serious reduction in the productivity of a process for manufacturing the connector. Moreover, the axial displacement of the pipe P.sub.1 in the collar 21 as a result of, for example, the vibration of an engine causes the wear of the seal ring 24 and thereby a lowering of its sealing property.
Another known connector is disclosed in Japanese Patent Publication No. 10711/1989. It comprises a housing 21 forming its main body and having a large-diameter chamber 22 and a small-diameter chamber 26, a pipe P.sub.1 extending into the housing 21 through its rear end having a flange 21', and having a radially outwardly projecting wall portion P.sub.1 ', a holding element 23 inserted in the large-diameter chamber 22 about the pipe P.sub.1, and having a pair of grip tabs 24 projecting from the housing 21, a mid-wall portion engaging the flange 21' and a pair of pawls 24' formed at its inner end and held against the wall portion P.sub.1 ' of the pipe P.sub.1 to hold the pipe P.sub.1 in position, as shown in FIG. 29. The small-diameter chamber 26 contains seal rings 25 formed from e.g. rubber, and held in contact with the pipe P.sub.1.
This device also has a number of drawbacks. The large-diameter chamber 22 of the housing 21 unavoidably has between the pipe P.sub.1 and the holding element 23 a large free space which is so large that the undesirable axial or radial movement of the pipe P.sub.1 is likely to result from any vibration transmitted to the connector and cause the abrasion or wear of the seal rings 25 which makes them incapable of maintaining a tight seal for a long period of time. It is likely that the holding element 23 may be disengaged from the projecting wall portion P.sub.1 ' of the pipe P.sub.1, if its grip tabs 24 projecting from the housing 1 are inadvertently contacted by anybody, or anything else, or receive any impact.